For many years it was quite common for service providers to utilize Time Division Multiplexing (TDM) switches to carry information, such as voice signals, across TDM-based data networks. In a typical TDM network arrangement, a TDM switch in the network converts voice signals from a telephone at a source end of a conversation into digitized voice information and places the digitized voice information into one or more TDM frames. The TDM frames are carried through the TDM network via a series of TDM switches to a destination endpoint. At the destination endpoint, a TDM switch extracts the digitized voice information from the TDM frames and converts it back to voice signals which are played on a telephone at the destination end of the conversation.
Nowadays, packet-based data networks are increasingly being employed to transport information contained in TDM frames over portions of TDM networks. The attractiveness of packet networks relates to their lower cost as well as their versatility. For example, with regards to versatility, many packet networks support the Internet Protocol (IP) which enables a number of other protocols, such as Voice over IP (VoIP) to be utilized on these networks. Further, IP is a base protocol that is used to communicate information across the Internet, thus packet networks open the possibility of using the Internet as a medium for transporting information normally carried by TDM networks.
Since many current-day communications networks operated by service providers have been built using TDM equipment, often service providers limit their deployment of packet networks within their TDM networks where it makes economic sense to do so. For example, a service provider may limit replacing portions of its TDM network containing fully depreciated TDM equipment with a packet network.
Because the format of TDM frames carried in the TDM network often differ from the format of packets carried in a packet network, gateway devices are often employed to “translate” between the TDM frames and the packets. Here, TDM frames are forwarded to a gateway device which reformats information contained in the frames, such as digitized voice information, into packets. These packets are then carried by packet switches in the packet network to another gateway device which reformats the information contained in the packets into one or more TDM frames, and transfers the frames over the TDM network.
The gateway devices may also be configured to further process the information contained in the TDM frames in an attempt to attain better bandwidth efficiency as well as enhance performance. For example, the gateway device may employ coder/decoders (CODECs) to perform various functions, such as detect voice activity-inactivity, remove silence, compress voice signals and process voice signals to cancel echo. Bandwidth efficiency may be attained by these functions as they tend to reduce the amount of information that is transported across the network.
One problem with processing information using CODECs, is that while being suitable for handling voice information, these techniques may not be suitable for handling data information, such as Short Message Service (SMS) text messages or data files. For example, a CODEC may remove silence from voice information contained in TDM frames by looking for a certain patterns in the voice information and if the pattern is found, dropping the voice information. While this may not be an issue for digitized voice as dropping small portions of a digitized voice signal may not be discernable to the human ear; this may be an issue for data information. For example, if the data information contains important transaction information, such as a bank transaction, dropping portions of the data may corrupt the transaction which could have drastic consequences.